I. Technical Field
The present invention relates generally to a viewing angle lens and, more particularly, to a viewing angle lens which changes the viewing angle of a vacuum fluorescent display of an accessory in a motor vehicle.
II. Disscusion
Typically, vehicle accessories are flush or recess mounted in the dashboards of automobiles at a level such that light emitted from the accessory display is projected horizontally into a vehicle occupant's midsection. As a result of this low level positioning, the vehicle occupant usually reads information provided by an accessory display at an angle; this angle is known as the viewing angle. By increasing the viewing angle, a manufacturer can either lower the positioning or increase the recess of the accessory on the dashboard. In the field of manufacturing, lower placement or recessed positioning of accessories on dashboards has certain manufacturing advantages. However, because of lower mounting, protrusions from the dashboard or walls of the cavity where the accessory is placed sometimes interfere with light being emitted at an angle from the accessory display. This can obstruct the vehicle occupant's view of the display. To allow the vehicle occupant to view the accessory, the viewing angle must be reduced or the accessory must be placed higher on the dashboard.
In an attempt to increase the viewing angle of a flush mounted accessory while not obstructing the vehicle occupant's view of the accessory, accessory displays, such as vacuum florescent displays, have been fitted with a display lens which has an index of refraction greater than 1. This lens bends the light emitted from the accessory horizontally while traveling through the lens. When the light exits the lens, it is bent back to its original viewing angle. In essence, the lens shifts the light outward by a distance proportional to the thickness of the lens. This shifting is designed to move the light outward, past any obstructions. Because the light is effectively shifted as a function of the thickness of the lens, thicker lenses allow greater shifting of light from an accessory.
However, certain problems exist in increasing the thickness of the display lens. First, some display lenses are tinted. Tinting is a process by which the clear plastic is colored with a darker material. This coloring causes the display lens to have a darker appearance. The darker appearance reduces the brightness of light which passes through it. By increasing the thickness of the display lens, the amount of tinted material is increased which greatly reduces the illumination of the vacuum florescent display. This illumination may be reduced to a point lower than what is acceptable for the vehicle occupant to read the information provided by the display. Second, conventional assembly methods in radio assembly place a limit on how thick the display lens can be. If the thickness of the display lens is to be increased past this limit, the display lens will no longer have a uniform thickness which will result in certain areas being thick and other areas being thinner. This non-uniform thickness is undesirable from a manufacturing standpoint. In the casting process, non-uniform thickness of materials which are being cast can create hot spots. These hot spots usually result in poor strength and quality characteristics. The present invention overcomes these drawbacks.